Oeological Society of London. 293 



priori have been expected ; and the nature of the test suggested that the Trilobites 

 were walking rather than swimming forms of Isopods. The branchia) had pro- 

 bably been under the telson ; and this would account for its large development. It 

 was not more surprising to find highly organized Trilobites than it was to find such 

 highly organized crustaceans as Pterygotus, Euryptvrus, and Slimonia in the same 

 beds. 



Prof. Rupert Jones, Principal Dawson, and Sir William Logan made some re- 

 marks, more especially on Protichnites and Climactichnites, the hitter having been 

 explained as galleries of Crustacea by Prof. Jones, when first exhibited in England. 



3. "On tlie Structure and Affinities of Sigillaria, Calamites, and 

 Calamodendron." By J. W. Dawson, LL.D., F.K.S., F-G.S., Princi- 

 pal and Yice-Cliancellor of M'Gill University, Montreal. 



The object of this paper was to illustrate the structure and affi- 

 nities of the genera above named, more especially with reference to 

 the author's previous papers on the " Structures in Coal," and the 

 " Conditions of Accumulation of Coal," and to furnish new facts 

 and conclusions as to the affinities of these plants. 



With reference to Sigillaria, a remarkably perfect specimen of the 

 axis of a plant of this genus, from the Coal-field of Nova Scotia, was 

 described as having a traversely laminated pith of the Sternhergia 

 type, a cylinder of woody tissue, scalariform internally, and reticu- 

 lated or discigerous externally, the tissues much resembling those 

 of Cycads. Medullary rays were apparent in this cylinder ; and it 

 was traversed by obliquely radiating bundles of scalariform vessels 

 or fibres proceeding to the leaves. Other specimens were adduced 

 to show that the species having this kind of axis had a thick outer 

 bark of elongated or prosenchymatous cells. The author stated 

 that Prof. Williamson had enabled him to examine stems found in 

 the Lancashire Coal-field, of the type of Binney's Sigillaria vascu- 

 laris, which differed in some important points of structure from his 

 specimens ; and that another specimen, externally marked like 

 Sigillaria, had been shown by Mr. Carruthers to be more akin to 

 Lepidodendron in structure. These specimens, as well as the Sigil- 

 laria elegans, illustrated by Brongniart, probably represented other 

 types of Sigillarioid trees, and it is not improbable that the genus Si- 

 gillaria, as usually understood, really includes several distinct generic 

 forms. The author had recognized six generic forms in a previous 

 paper, and in his " Acadian Geology ;" but the type described in 

 the present paper was that which appeared to predominate in the 

 fossil Sigillarian forests of Nova Scotia, and also in the mineral 

 charcoal of the coal-beds. This was illustrated by descriptions of 

 structures occurring in erect and prostrate Sigillaria, on the surface 

 of Sternbergia-GcLSts, and in the coal itself. 



The erect Calamites of the coal fonnation of Nova Scotia illus- 

 trate in a remarkable manner the exterior surface of the stems of 

 these plants, their foliage, their rhizomata, their roots, and their 

 habit of growth. Their affinities were CAadently with Equisetaceae, 

 as Brongniart and others had maintained, and as Carruthers and 

 Schimper had recently illustrated. The internal structure of these 

 plants, as shown by some specimens collected by Mr. Butterworth, of 

 Manchester, and soon to be published by Prof. Williamson, showed 



